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Calibration Procedure Teledyne API Model M201E NH
3
Analyzer Operator Manual
20 05206H DCN5910
2.3 SPANNING THE ANALYZER WITH AMMONIA GAS
The most important criterion an individual can avail themselves of when spanning
an analyzer with
ammonia gas is “patience”. Ammonia is a very sticky gas and
the response of the analyzer/calibration system depends on a number of factors.
The following lists some important points the user should be aware of when
calibrating:
Is this the first time the analyzer/calibration system has seen
ammonia gas
in the last couple of days? If so, spanning to a fixed value will take
considerably longer than normal: possibly 12 hours to completely stabilize.
Is the tubing that is delivering span gas from the calibration bottles, made
of stainless steel? Is the tubing from the rear of the calibrator to the
analyzer, made of stainless steel? Where possible use stainless steel
tubing.
Note: The operator is responsible for delivering a set amount of
ammonia
to the analyzer, calculating the converter efficiency of the M501 NH
3
, and
entering the efficiency value through the user interface, if required.
Is the environment where the analyzer resides undergoing large
temperature swings (+/- 5 C about the norm Temperature)? If so the
sample line can absorb and desorb
ammonia at concentration rates that
are distinguishable to the analyzer. If possible, heat the sample line to a
constant maximum ambient temperature. Otherwise the FILT_SIZE = 42
Samples variable located under the VARS MENU can be lengthened.
However, lengthening the filter size slows the rise/fall response time of the
analyzer.
Does the sampling environment contain large amounts of particulates? If
so, it may be necessary to add the sampling filter option. As outlined
previously, this will affect the analyzer response.
One method to increase the response of both the sampling system and
the analyzer is to flow a larger concentration of
ammonia gas through the
pneumatics for a couple of hours. For example, if the expected range is
500 PPB of ammonia, then flowing 1.0 PPM speeds up the absorption
which occurs throughout the pneumatics. The long delays in
ammonia
response occur when the analyzer hasn’t sampled the gas for some time.
Ammonia desorbs from the pneumatics, these surfaces need to be
rewetted before span stability is achieved.
Prior to conducting the ammonia calibration, confirm that the ammonia
converter efficiency is initially set to 1.000 using the following menu key
selections: